The hitherto known linear ball bearing is usually constructed such that side covers and retainer are separately manufactured and then assembled onto a bearing casing (c.f. U.S. Pat. No. 4,253,709).
The conventional retainer is made of steel plate by press working in such a manner that a plurality of longitudinally extending slits are punched out at predetermined positions and at the same time considerably small tongue pieces are projected out at both the ends of the respective slits for the purpose of ensuring scooping function for the rolling balls. To meet this requirement it is necessary that the tongue pieces have high mechanical strength and wear resistance.
For the reason the conventional retainer is made of steel plate having excellent rigidity and resiliency and after completion of press working it is subjected to heat treatment, which causes it to be manufactured at an expensive cost.